Where two ends of a cable such as a telecommunications cable are spliced together, the splice area is ordinarily housed within a protective cover known as a closure. Common to substantially all closures is the requirement that they restrict moisture ingress. The integrity of seals which are used to restrict moisture ingress is important especially because of transmission parameters which are readily effected by changes in the moisture content within the cable. Also, common to most closures is the provision of some degree of cable strain relief to prevent splice separation.
Such closures often have included cylindrical covers with one or more longitudinal joints and end plates that surround incoming and outgoing cables and that form seals with the covers. An example of a prior art closure is shown in U.S. Pat. No. 3,636,241 which issued on Jan. 18, 1972 in the names of R. G. Baumgartner et al. Closures which are effective in providing protection for the splice connections are available in the marketplace, but their assembly is relatively time consuming, often requiring specialized tools and equipment which in a limited space such as an underground tunnel are difficult to handle and operate.
To prevent moisture ingress, some systems employ dry air, nitrogen or a similar chemically inert gas in the cables and closures. In this type of reenterable closure, the gas is pressurized to create a flow from enclosed equipment through any openings and prevent the ingress of moisture. In such a system, it is advantageous to minimize the amount of gas leakage to reduce the consumption of pressurized gas and to insure against any requirement of high gas flow to maintain adequate pressure throughout the system. Accordingly, closures and associated equipment should be sealed sufficiently to prevent a reduction in pressure and the loss of gas. At the same time it is necessary to provide a system which is easily assembled in the field and in which the probability of installer error is relatively low.
Heretofore a number of sealed closure designs have been made available. However, most of these have employed complicated sealing mechanisms which have a high probability of installer error and which consume much time. One major problem with earlier designs has been the need for close tolerances and interference fits. Mechanisms requiring close tolerances and interference fits often are easily damaged in the field where assembly is performed, are expensive to fabricate, and also may require close attention to assembly. These considerations add significantly to both the initial cost of the closure and to the cost of its assembly in the field. Despite their design, such closures may still admit moisture where they are improperly assembled. A closure in which the covers are easily assembled and which provides an effective sealing system with relatively low craft sensitivity is disclosed and claimed in copending commonly assigned application Ser. No. 597,679 which was filed on even date herewith in the name of J. R. Massey.
Although the problems of sealing a closure and of cover assembly have been overcome by the closure of the above-identified application, problems which relate to the end plate remain unsolved. Typically, a cable enters the closure through an opening formed between mating portions which are assembled to form the end plate. As can be seen in U.S. Pat. No. 4,295,005, which issued on Oct. 13, 1981 in the names of E. E. Daugherty et al., the entry of the cable into the closure is sealed by wrapping the cable with a plurality of convolutions of a sealing tape between two retaining washers. The tape and washers are held between end flanges of mating cover portions or are held within the wall of the opening in the end plate through which the cable extends. In one typical symmetrical end plate which comprises two mating portions, fasteners must be applied to each side of the assembled portions to secure them together and to apply a balanced force system to the sealing tape disposed in the opening formed between the two portions. Inasmuch as some of these fasteners are disposed on the outside of the closure, they must be made of a corrosion-resistant material. Other cable entrance designs are available, but they involve complicated molding techniques. For example, in U.S. Pat. No. 4,361,721, each entrance passageway for a cable includes a plurality of longitudinally spaced circumferential ridges. Each ridge is capable of flexing to enlarge the passageway to form a radial seal about a cable being inserted.
Another problem with prior art end plates relates to the strain relief for cables entering the closure. As the outer diameter of the entering cable decreases, the strain relief facilities which may form part of the end plate must extend farther from the end plate in a radial direction to engage the cable. Although some systems which are available in the marketplace provide effective strain relief for large size cables, they have insufficient mechanical strength to span greater distances from their support by the end plate to engagement with a relatively small pair size cable.
The prior art does not seemingly include a relatively inexpensive, reliable closure end plate for use over splices of pressurized communications cables, for example, which allows reentry to the splices and subsequent reassembly. There is still a need for such a closure end plate. Such an end plate is desirable where future changes will be required in the splice connections or where strong possibilities of such changes exist. Further, the end plate assembly should be one which provides an effective seal about the entering cable and and effective strain relief for the cable splice.